Referring to the article https://blog.angularindepth.com/everything-you-need-to-know-about-the-expressionchangedafterithasbeencheckederror-error-e3fd9ce7dbb4
So the mechanics behind change detection actually works in a way that both change detection and verification digests are performed synchronously. That means, if we update properties asynchronously the values will not be updated when the verification loop is running and we will not get ExpressionChanged... error. The reason we get this error is, during the verification process, Angular sees different values then what it recorded during change detection phase. So to avoid that....
1) Use changeDetectorRef
2) use setTimeOut. This will execute your code in another VM as a macro-task. Angular will not see these changes during verification process and you will not get that error.
setTimeout(() => {
this.isLoading = true;
});
3) If you really want to execute your code on same VM use like
Promise.resolve(null).then(() => this.isLoading = true);
This will create a micro-task. The micro-task queue is processed after the current synchronous code has finished executing hence the update to the property will happen after the verification step.